1. Field of the Invention
The subject invention relates to a hose construction. More specifically, the subject invention relates to a hose assembly having an inner fluoropolymer layer with a polyamide outer layer used in automotive, aeronautics and other environs for carrying fluids, such as fuels.
2. Description of Related Art
Hose assemblies for conveying fuels are well known in the art. Such assemblies are exposed to a variety of fuel mixtures and fuel additives in addition to extreme engine temperatures. Such hose assemblies must be resistive to chemicals, as well as heat resistant to degradation as a result of chemical and heat exposure.
Fluoropolymer materials, such as polytetrafluoroethylene possess the requisite chemical and temperature resistant properties for most fuel hose applications. However, fluoropolymer materials exhibit relatively poor tensile and hoop strengths. As a consequence, such fluorinated materials are prone to kinking. Such kinking remains permanent and provides a continual resistance to fluid flow through the hose assembly. Moreover, as a result of the fluorinated material low tensile strength, attachment of securing or coupling members to the hose assembly is unreliable.
Various approaches have been described for offering additional strength to a fluoropolymer layer. One approach involves braiding fibers about the inner fluorocarbon layer. The braided fibers offer additional strength for the fluorocarbon layer resulting in a hose assembly that resists kinking. An example of such an approach is disclosed in co-pending U.S. Ser. No. 08/535,734, filed Jun. 11, 1990, and assigned to the assignee of the subject invention. A drawback of such braiding techniques, however, is the extensive labor and time involved.
Additional examples for strengthening an inner fluorocarbon layer with an outer layer are shown in U.S. Pat. No. 2,991,808 to Sigmann, U.S. Pat. No. 4,104,095 to Shaw, and U.S. Pat. No. 4,800,109 to Washizo, all of which disclose the use of a polytetrafluoroethylene inner layer supported with an outer layer.
Alternatively, some patents in the prior art utilize both an outer layer and a braided layer for added strength as shown in U.S. Reissue Pat. No. 35,527. However, there remains problems with the bending capabilities of such tubing in conjunction with the outer layer.
Furthermore, some patents in the prior art utilize multi-layer hoses with corrugated outer surfaces for added strength at the bending sites, as shown in the U.S. Pat. No. 5,305,799, to Holmgren. However, these processes have not been utilized for hoses having an inner fluoropolymer layer and an outer polyamide layer.
Additionally, some patents in the prior art utilize machines for creating corrugation, as shown in the U.S. Pat. No. 3,864,446, to Maroschak. However, there remains problems in creating corrugation without having to corrugate the entire hose assembly.
It would therefore be useful to develop a hose which is resistant to kinking when being bent without adding extensive labor or time to the manufacturing process.
According to the present invention, there is provided a hose assembly with an inner fluoropolymer layer having a smooth inner surface and an outer polyamide layer having an undulated surface. A method is provided for making a hose assembly by forming a smooth inner fluoropolymer layer without undulations and an outer polyamide layer having undulations.